PRELIMINARY DYNAMO Gan ARM Radiosonde Data

1.0 General Description

This is one of the upper air data sets developed for the Dynamics of the Madden-Julian Oscillation (DYNAMO) 2011-2012 project. This preliminary data set includes 1068 high vertical resolution (2-sec) soundings from the Atmospheric Radiation Measurement (ARM) M1 Airport (Addu Atoll), Gan Island, Maldives site, collected during the DYNAMO field campaign from 22 September 2011 through 9 February 2012. There are typically eight soundings per day at 00, 03, 06, 09, 12, 15, 18, and 21 UTC. This preliminary version of the data set contains data from 22 September 2011 to 9 February 2012. There may be corrections applied to these data at a later point. If you order this data set now you will be notified when additional and/or corrected data becomes available. After 9 February 2012 the Maldivian Meteorological Service continued to conduct releases once or twice per day through the end of the DYNAMO field phase. Those data will be part of a separate data set.
This station used Vaisala RS92-SGP radiosondes with GPS windfinding during the DYNAMO field campaign.

1.1 Data Set Contact

Scot Loehrer
NCAR/EOL
loehrer@ucar.edu

1.2 Detailed Site Information

The following information was provided by Chuck Long (PNNL) about the Gan release site and surface station.

Sondes used are RS-92 using Digicora V3.64 software. This software includes proprietary daytime dry bias correction for RH and applies the Vaisala smoothing algorithm. The details of these algorithms are proprietary to Vaisala. All sondes prepped using a GC25 unit inside an air-conditioned van. Balloons use helium gas with the sonde package set on an open-air, non-forced-air-aspirated shelf during balloon filling prior to launch.

Surface data entered in to the Digicora software come from AMF-1 met system, using forced-air aspirated Vaisala HMP45 combined T/RH probe located about 50 feet from balloon filling station. Generally good agreement between these met measurements and sonde values at launch time.

2.0 Detailed Data Description

2.1 Detailed Format Description

All upper air soundings were converted to National Center for Atmospheric Research/Earth Observing Laboratory (NCAR/EOL) Sounding Composite Format (ESC). ESC is a version of the National Center for Atmospheric Research (NCAR) CLASS format and is an ASCII format consisting of 15 header records for each sounding followed by the data records with associated QC information.

Header Records

The header records (15 total records) contain data type, project ID, site ID, site location, release time, sonde type, and meteorological and wind data processors. The first five header lines contain information identifying the sounding, and have a rigidly defined form. The following 7 header lines are used for auxiliary information and comments about the sounding, and may vary from dataset to dataset. The last 3 header records contain header information for the data columns. Line 13 holds the field names, line 14 the field units, and line 15 contains dashes ('-' characters) delineating the extent of the field.

Longitude in deg min is in the format: ddd mm.mm'W where ddd is the number of degrees from True North (with leading zeros if necessary), mm.mm is the decimal number of minutes, and W represents W or E for west or east longitude, respectively. Latitude has the same format as longitude, except there are only two digits for degrees and N or S for north/south latitude. The decimal equivalent of longitude and latitude and station elevation follow.

The seven non-standard header lines may contain any label and contents. The labels are padded to 35 characters to match the standard header lines. Records for this dataset include the following non-standard header lines.

Line

Label (padded to 35 char)

Contents

6

Sonde Id/Sonde Type:

G0220143/Vaisala RS92-SGP with GPS windfinding

7

8

9

10

11

12

Nominal Release Time (y,m,d,h,m,s):

Nominal time of release, in the format: yyyy, mm, dd, hh:mm:ss

Data Records

The data records each contain time from release, pressure, temperature, dew point, relative humidity, U and V wind components, wind speed and direction, ascent rate, balloon position data, altitude, and quality control flags (see the QC code description). Each data line contains 21 fields, separated by spaces, with a total width of 130 characters. The data are right-justified within the fields. All fields have one decimal place of precision, with the exception of latitude and longitude, which have three decimal places of precision. The contents and sizes of the 21 fields that appear in each data record are as follows:

Field No.

Width

Format

Parameter

Units

Missing Value

1

6

F6.1

Time

Seconds

9999.0

2

6

F6.1

Pressure

Millibars

9999.0

3

5

F5.1

Dry-bulb Temperature

Degrees C

999.0

4

5

F5.1

Dew Point Temperature

Degrees C

999.0

5

5

F5.1

Relative Humidity

Percent

999.0

6

6

F6.1

U Wind Component

Meters / Second

9999.0

7

6

F6.1

V Wind Component

Meters / Second

9999.0

8

5

F5.1

Wind Speed

Meters / Second

999.0

9

5

F5.1

Wind Direction

Degrees

999.0

10

5

F5.1

Ascent Rate

Meters / Second

999.0

11

8

F8.3

Longitude

Degrees

9999.0

12

7

F7.3

Latitude

Degrees

999.0

13

5

F5.1

Elevation Angle

Degrees

999.0

14

5

F5.1

Azimuth Angle

Degrees

999.0

15

7

F7.1

Altitude

Meters

99999.0

16

4

F4.1

QC for Pressure

Code (see below)

99.0

17

4

F4.1

QC for Temperature

Code (see below)

99.0

18

4

F4.1

QC for Humidity

Code (see below)

99.0

19

4

F4.1

QC for U Wind Component

Code (see below)

99.0

20

4

F4.1

QC for V Wind Component

Code (see below)

99.0

21

4

F4.1

QC for Ascension Rate

Code (see below)

99.0

Fields 16 through 21 contain the Quality Control information derived at the NCAR Earth Observing Laboratory (NCAR/EOL). Any QC information from the original sounding is replaced by the following EOL codes:

Code

Description

99.0

Unchecked (QC information is "missing.") ("UNCHECKED")

1.0

Checked, datum seems physically reasonable. ("GOOD")

2.0

Checked, datum seems questionable on physical basis. ("MAYBE")

3.0

Checked, datum seems to be in error. ("BAD")

4.0

Checked, datum is interpolated. ("ESTIMATED")

9.0

Checked, datum was missing in original file. ("MISSING")

Sample Data

The following is a sample record of DYNAMO Gan ARM high resolution sounding data in ESC format. The data portion is much longer than 80 characters and, therefore, wraps around to a second line. See section 2.1 for an exact format specification.

2.2 Data Remarks

2.3 Station List

ID

SITE

LONG

LAT

ELEV (m)

Gan_ARM

M1 Airport, Gan Island, Maldives

73.150

-0.690

1.0

3.0 Quality Control Processing

This dataset underwent an automated QC process. The dataset underwent
internal consistency checks which included two types of checks, gross limit
checks on all parameters and rate-of-change checks on temperature, pressure and
ascension rate. Some further information on the QC processing conducted by
NCAR/EOL can be found in Loehrer et al. (1996) and Loehrer et al. (1998).

3.2 Vertical Consistency Checks

These checks were conducted on each sounding and data were automatically
flagged as appropriate. These checks were started at the lowest level of the
sounding and compared neighboring 2-sec data points (except at pressures less
than 100 mb where 30-sec average values were used). In the case of checks
ensuring that the values increased/decreased as expected, only the data point
under examination was flagged. However, for the other checks, all of the data
points used in the examination were flagged. All items within the table are
as previously defined.

3.3 Visual Quality Checks

Each sounding was visually examined for data quality issues. Any issues
found were flagged in the data file and/or noted in Section 3.4.

3.4 Data Quality Issues

There are low level temperature, humidity, and surface station data issues that are being examined at this station.

Some soundings exhibit seeming oscillations in the RH data. This sometimes occurs during periods of slow (< 3m/s) balloon ascent due to the cycling of the dual VRS92 humidity sensors. Examples can be seen in the following soundings: